1. Field of the Invention
The present invention relates to various approaches for processing an ongoing stream of digital samples which, when employed together, are suitable for use in a vestigial-sideband (VSB) digital modulator that derives a 6 MHz bandwidth input signal selectively centered either at 63 MHz (Channel 3), 69 MHz (Channel 4) or 5.38 MHz IF (baseband) for a television receiver and, more particularly, for a compressed digital television receiver or set top box. Related applications filed concurrently herewith are SIN(X)/X COMPENSATION CIRCUITRY Ser. No. 09/382,235; COMPLEX MODULATOR CARRIER SIGNAL GENERATOR Ser. No. 09/382,234; and A PULSE CODE MODULATED TO DC CENTERED VSB CONVERTER RCA Ser. No. 09/382,232.
2. Description of the Prior Art
Reference is made to the article xe2x80x9cATSC Re-modulator Systemxe2x80x9d by Hauge et al., IEEE Transactions on Consumer Electronics, Vol. 44, No. 3, August, 1998. This article discloses a VSB digital re-modulator implementation to interconnect between various digital products (e.g., terrestrial digital broadcasting, satellites, digital cable set top boxes, cable modems, DVD, DVCR, PC""s, etc.) and digital TV receivers. Such a VSB digital re-modulator is the digital equivalent to current analog re-modulators found in VCR""s and video games.
There is a need for a simpler and, hence, less expensive approach capable of providing an integrated-circuit (IC) implementation of a VSB digital re-modulator that selectively derives a Channel 3, Channel 4 or baseband signal.
The present invention is directed to a digital method and apparatus for modulating a stream of digitized samples from a source, by a digital representation of a carrier to provide, for example, a 6 MHz bandwidth television signal selectively centered either at 63 MHz (Channel 3), 69 MHz (Channel 4) or 5.38 MHz IF (baseband). More particularly the method includes first resampling the stream of digitized samples and then modulating the resampled stream of samples with a repeating short sequence of complex values, which complex values represent a digitized exponential carrier.